Preparation of 1, 7-octadiene



United States Patent 3,388,182 PREPARATION OF 1,7-0CTAD1ENE Samuel W. Tinsley and Edward A. Rich, South Charleston, W. Va., assignors to Union Carbide Corporation, a corporation of New York No Drawing. Filed May 12, 1961, Ser. No. 109,488

- 6 Claims. (Cl. 260-680) This invention relates to a novel process for the production of 1,7-octadiene in good yields and high efliciencies.

More particularly, this invention relates to the production of 1,7-octadiene by the pyrolysis of cyclooctene.

1,7-octadiene is a well known compound which has potential uses in many commercial applications including the manufacture of vinyl resins. Recently, 1,7-octadiene has been used as a starting material for the preparation of 1,2:7,8-diepoxyoctane, said epoxy being particularly useful in the preparation of epoxy resins.

3,388,182 Patented June 11., 1968 can vary over a very broad range. Thus, it is possible to use from 2 percent to 300 percent by weight of the diluent based on the total amount of cyclooctene employed.

The following examples will illustrate the novel process of this invention.

Examples 1-7 TABLE I Efiluent Example N Flow, Cyclooctene Yield 1,7- Efiieiency,

N 0. 'I., C. l./rnin. Chargeg Percent Percent octadicne, percent grams Grams Cyclo- 1,7-octapercent octene diene Purity of starting material as determined by vapor phase chromatography: 88.7%. b Cyclooctene was dripped directly into the pyrolysis tube.

The prior art processes for the manufacture of 1,7- octadiene have been expensive to install, costly to maintain and, in general, the yields an deificiencies obtained were not very good.

Accordingly, it is the primary object of this invention to provide a novel process for the preparation of 1,7- octa-diene, said process being eflicient, economical and utilizing a readily available starting material.

The process of this invention is carried out simply by pyrolyzing cyclooctene at a temperature within the range of 450-700 C. It is to be understood that the novel process can be carried out in both batch and continuous processes, said continuous process being preferred for commercial operations. It should :also be understood that the process is not limited to operation at atmopsheric pressure, but may also be carried out at subatmosp'heric or superatrnospheric pressures.

As heretofore pointed out, the process of this invention is carried out at temperatures from 450700 C. However, the preferred temperature range is from 500-600 C. since within these ranges higher yields and/or efficiencies are obtained.

The contact time of the cyclooctene in the reaction chamber is not narrowly critical and contact times from 1 second to 30 seconds are operable. However, it is preferred to employ contact times of fnom 2 to 10 see onds since higher yields and/or efliciencies are obtained at these contact times.

In another aspect of this invention, it is possible to conduct the pyrolysis of cyclooctene in the presence of an inert diluent. The particular diluent employed is not critical and any diluent which is inert under the conditions of the reaction is operable. Typical diluents which are operable in the novel process of this invention include water, nitrogen, helium, argon, etc. The preferred diluent is water.

The .amount of diluent employed in relation to the total amount of cyclooctene employed is also not critical and The 1,7-octadiene was isolated by fractional distillation of the tube effluent. The material thus obtained had the following physical properties: B.P. 119 C.; n 1.4166.

Analysis for C l- Calculated: C, 87.19; H, 12.81. Found: C, 87.40; H, 12.77.

Example 8 Cyclooctene (159 grams/hour) and water (45 grams/ hour) were pumped into the pyrolysis tube. This tube, a 1" x 48 stainless steel tube packed With 6 mm. glass beads, was maintained at a temperature of 550 C. by immersion in an electrically heated salt bath. The tube effluent was condensed and subsequently distilled to give a 1,7-octadiene in 24.5 percent yield with an efficiency of 83.8 percent.

Example 9 Cyclooctene (260 grams/ hour) and water grams/ hour) were pumped into the pyrolysis tube described in Example 8. With the tube maintained at 600 C. there was obtained a 39 percent yield of 1,7-octadiene at an efficiency of 72 percent.

Example 10 Cyclooctene was mixed with water, passed through a preheater and then pyrolyzed at 550 C. in a 196 foot tube (0.662 inches I.D.). Tube effluents were condensed, the water layer was removed and the organic material was analyzed by vapor phase chromatography. The results of these experiments are summarized in the table below:

TABLE II 1. The process of preparing 1,7-octadiene which comprises pyrolyzing cyclooctene at a temperature of from 4507 00 C. at a contact time of from 1 to 30 seconds.

2. The process of preparing 1,7-octadiene which comprises pyrolyzing cyclooctene in the presence of water at a temperature of from 500-600 C. at a contact time of from 2 to 10 seconds.

3. A process which comprises pyrolyzing cyclooctene at a temperature of from 450 to 700 C. for a period of time sufiicient to produce 1,7-octadiene.

4. The process of claim 3 wherein the temperature is from 500 to 600 C.

5. A process which comprises pyrolyzing cyclooctene in contact with an inert diluent, at a temperature of from 450 to 700 C. and for a period of time sufiicient to produce 1,7-octadiene.

6. The process of claim 5 wherein said inert diluent is water.

References Cited UNITED STATES PATENTS 2/1940 Rice 260-680 1/1946 Watson 260-680 X ALPHONSO D. SULLIVAN, JAMES S. BAILEY, MIL- TON STURMAN, Examiners.

C. E. SPRESSER, JR., Assistant Examiner. 

1. THE PROCESS OF PREPARING 1,7-OCTADIENE WHICH COMPRISES PYROLYZING CYCLOCTENE AT A TEMPERATURE OF FROM 450-700*C. AT A CONTACT TIME OF FROM 1 TO 30 SECONDS. 